1. Field of the Invention
The invention relates to a method and apparatus for generating optimum write power, more particularly to a method of using hardware circuits to execute and control an optimum write power generating process and to automatically employ a series of powers to perform interval-wise test recording so as to obtain parameters of characteristics of the recording power of each interval to thereby determine the optimum write power, and an apparatus therefor.
2. Description of the Related Art
In an optical recording system, an optical read/write head is mainly used to produce a laser beam. The laser beam is a write signal generated as a result of modulation of digital data to be recorded so as to form light readable pits that represent digital data on an optical disk to be recorded. Therefore, the laser power of the write signal becomes one of the important factors that determine the recording quality of the optical disk. Thus, how to control the optical read/write head to output the optimum write laser power becomes an important technique in the field of optical storage techniques.
At present, conventional optimum write power generating methods mainly fall into two types. One is the pre-recording optimum power control (OPC) technique, in which an optical recording system uses a series of write powers (i.e., a plurality of different write powers) to perform a recording test (test recording) in a predetermined test area of the optical disk before proceeding with the actual recording, and to subsequently obtain a read reflected (RRF) signal by reading light readable pits recorded on the test area. Each of the read reflected signals is analyzed and determined so as to select therefrom a write power that produces the best recording quality (i.e., generating the optimum light readable pits) for performing the actual data recording on the optical disk.
The other is the running optimum power control (ROPC) technique, in which the optical recording system, during the actual recording process, acquires a write reflected (WRF) signal generated by a write signal and, after analysis and determination of the same, generates in real time an optimum write power to replace the previous write signal, thereby enabling the optical recording system to always maintain the optimum recording quality during the recording process.
Whether it is the OPC technique or the ROPC technique, either will generate some relevant parameters representing the quality of the write power when the RRF signal and the WRF signal are analyzed and computed. For instance, the OPC technique will generate β parameters, and the ROPC technique will generate α parameters. Therefore, the optical recording system may select the pre-recording or running optimum write power based upon these parameters. Thus, if there are good OPC and ROPC process control and good parameter computing methods, optimum control of the write power of the optical storage device can be achieved.
However, in the traditional OPC execution procedures, a microprocessor built in the system uses a software program to control operation of the existing memory and I/O addresses to continuously generate a plurality of write voltages of different levels, and to drive the optical read/write head to generate a plurality of different write laser powers to perform test recording on a test area of the optical recording medium in sequence, followed by reading of the light readable pits recorded on the test area so as to obtain a plurality of corresponding read reflected (RRF) signals. Based on the RRF signals, an optimum control parameter β is obtained, and an optimum write laser power is generated based thereon. Therefore, the microprocessor needs to spend a considerable amount of time in computing the OPC values. However, in addition to performing OPC control, the microprocessor also needs to perform synchronous control of other servo mechanisms in the optical recording system, e.g., the motor rotational speed, the focus and track-locking of the optical read/write head, encoding, etc., so that the microprocessor is overloaded and cannot produce a good working efficiency, and cannot quickly generate the optimum write power control parameters required by OPC.
In addition, in the current optical recording system, the microprocessor is not equipped with both OPC control and ROPC control. That is, the microprocessor can only select using one of OPC control and ROPC control. Therefore, the microprocessor cannot execute ROPC to obtain the control parameter α when executing OPC (to generate the control parameter β).
Accordingly, how to reduce the workload of the microprocessor, how to establish a quick and automatic OPC procedure executing mechanism, and how to simultaneously carry out ROPC during the process of executing the OPC procedure so as to obtain the optimum write power control parameters have become the technical emphasis of this invention.